As is well known, a fuel cell is an electricity generating system for generating electric energy through an electrochemical reaction between oxygen and hydrogen contained in hydrocarbon materials such as methanol, ethanol, and natural gas.
Recently developed polymer electrolyte membrane fuel cells (hereinafter, referred to as PEMFCs) have excellent output characteristics, low operating temperatures, and fast starting and response characteristics. Therefore, PEMFCs have a wide range of application including use as mobile power sources for vehicles, as distributed power sources for homes or buildings, and as small-sized power sources for electronic apparatuses.
A fuel cell system employing a PEMFC scheme basically includes a stack, a reformer, a fuel tank, and a fuel pump. The stack constitutes an electricity generator set having a plurality of unit cells. The fuel pump supplies fuel stored in the fuel tank to the reformer. Then, the reformer reforms the fuel to generate hydrogen which is supplied to the stack.
In a conventional fuel cell system, the reformer generates hydrogen from the hydrogen-containing fuel through a catalytic chemical reaction using thermal energy. Accordingly, the reformer generally includes a heat source section for generating the thermal energy, a reforming reaction section for absorbing the thermal energy and generating hydrogen gas from the fuel, and a carbon-monoxide reducing section for reducing the concentration of carbon monoxide in the hydrogen gas.
In a conventional reformer, since the heat source section, the reforming reaction section, and the carbon-monoxide reducing section are distributed and connected through pipes, the heat exchange between the reaction sections is inefficient from the view point of heat delivery.
In addition, since the respective reaction sections are distributed, it is difficult to make the entire fuel cell system compact. Moreover, the complex structure of the pipes used in interconnecting the sections complicates manufacturing.